Hi,

Thanks all for the replies, the boiler is only 8.8kw and 30,000 BTU/H
if that changes things?

Incidently, my boiler does kettle a bit but isnt too bad, we will see
if the flush and treatment helps.

I have noticed a few of the radiator valves are weaping a bit so I need
to look at that too.

I will try the screwfix route for flush and treat before going the
whole hog on hiring the kit to do a DIY powerflush I think.

Is it ok to replace the radiator valves? My dad is pretty confident we
can do it easily enough and I want to put two TRVs on the bedroom
radiators if I can anyway. So while I am draining the whole system it
may be just as well to replace the weapy valves.

Is there anything I need to know about TRVs, Valves with respect to my
10mm plastic pipe or should they (screwfix, toolstation ones) be ok to
fit?

My dad has fitted my TRVs on 10mm metal pipe but he is little unsure of
the plastic type.

Thanks again,

Mike